CNC-cutting the sides to shape before bending worked surprisingly well. I had left 10mm extra at each end, but that turned out to be unnecessary. The back will have a 3000mm radius and the top will be bent slightly inwards for stability.
No, that's not the issue, I thought it was a typo. A 3 meter radius for the back... im not sure what you mean but it sounds way too large for a guitar, whatever the measurement is for.